This invention relates to a thin multi-terminal capacitor for use in stabilizing a power supply voltage of an electronic device and reducing high-frequency noise thereof and a method of manufacturing such a capacitor and, in particular, relates to a thin multi-terminal capacitor suitable to be disposed and operated inside or near a semiconductor plastic package and a method of manufacturing such a capacitor.
In microprocessors, digital signal processing LSIs, or the like for use in personal computers, servers, digital household electric appliances, communication devices, and so on, the operating speed has been increasing in recent years, wherein a capacitor with a large capacitance and a low impedance is used in a power circuit for stabilizing the power supply voltage and reducing the high-frequency noise. In order to satisfy such requirement for the large capacitance and low impedance, a plurality of capacitors may be connected in parallel so as to achieve a required capacitance and impedance. On the other hand, Japanese Unexamined Patent Application Publication JP-A 2004-80733 discloses a technique of forming a transmission line type noise filter that realizes the large capacitance and low impedance with a single element and can withstand high current.
However, when the transmission line type noise filter described in JP-A 2004-80733 is used in a high-frequency region of several GHz or more, the inductance caused by wiring between a semiconductor device and the transmission line type noise filter exerts an influence. Further, when the transmission line type noise filter is used so as to be connected to a solder ball connection type semiconductor device, the inductance caused by wiring between the semiconductor device and the transmission line type noise filter exerts an influence even if used in a frequency region not exceeding several GHz. In order to avoid such an increase in inductance due to the drawing of wiring to achieve a reduction in impedance in the mounted state, it is necessary to implement precise positioning between electrode terminals of the transmission line type noise filter and power supply terminals of the semiconductor device so that difficulties are encountered in the mounting.
As a capacitor capable of avoiding the increase in inductance due to the drawing of wiring, there is a capacitor of the type that can be used while disposed inside or near a plastic package of a semiconductor device. For example, Japanese Unexamined Patent Application Publication JP-A 2004-71589 discloses a thin-film capacitor that is adapted to be incorporated in a wiring board or a semiconductor integrated circuit and has a structure of relaxing the internal stress so that the initial properties of the capacitor immediately after the fabrication thereof does not change even after the incorporation. This capacitor has a resonant frequency of several GHz or more and serves as a highly reliable decoupling capacitor.
However, JP-A2004-71589 discloses the technique that is applicable to a thin-film capacitor using a capacitance insulating film typically made of Ta2O3, SrTiO3, or the like. Specifically, this thin-film capacitor contributes to a reduction in power supply noise as a decoupling capacitor but has a capacitance of only about 1000 pF and, therefore, should be used along with large-capacitance capacitors in order to cope with noise caused by fluctuation in power supply voltage. Since it is impossible to place all those large-capacitance capacitors in a semiconductor plastic package, most of them are left on a board. Therefore, it is necessary to dispose, in the semiconductor package, a capacitor having a capacitance necessary for preventing a time delay in charge supply from a power supply due to the inductance caused by drawing of wiring between the capacitors on the board and a semiconductor device in the semiconductor package.
Further, as seen also from JP-A2004-71589, in order to cope with the high-frequency region of several GHz or more, it is not enough only to dispose the capacitor inside or near the semiconductor package but it is also necessary to reduce the thickness of the capacitor as much as possible so as to minimize drawing of wiring. However, when the structure is thin, it is weak against bending stress and, at the time of mounting by reflow soldering or the like, degradation in properties, such as an increase in leakage current (LC), tends to occur due to heat stress or the like.